1. Field of the Invention
This invention relates to data storage subsystems and, in particular, to an improved process for assuring data integrity when writing data to storage subsystems that use redundancy information.
2. Related Art
The method of the present invention may be advantageously used in conjunction with the methods and apparatus of the data storage subsystem disclosed in U.S. Pat. No. 5,124,987 issued to Charles A. Milligan, et al. Milligan, et al., discloses a data storage subsystem that utilizes an array of parallel disk drives to improve performance and reliability of the data storage subsystem. Data is generated external to a cache component of the data storage subsystem and applied to the cache component. Redundancy information is automatically generated by the cache component. The cache component controllably writes the externally generated data and internally generated redundancy information to a plurality of disk drives in the array. The redundancy information is used by the storage subsystem control unit to recover lost information in case of a failure of a limited number of the disks in the array of disk drives. Milligan, et al., discloses a method for improving the performance of such a storage subsystem by reducing the number of read and write operations required to update the stored redundancy information.
U.S. Pat. No. 5,146,588 issued to Michael R. Crater, et al., discloses further performance enhancements to a storage subsystem similar to that described by Milligan, et al. Crater, et al., teaches a method for avoiding time-consuming reset sequences for a redundancy generator circuit such as may be utilized in the data storage subsystem of the present invention.